Takifugu Obscurus Research Articles

Relationship Between Time of Insemination Postovulation and Fertilization Rate of Eggs of Obscure Puffer Fish, Takifugu obscurus

Relationship Between Time of Insemination Postovulation and Fertilization Rate of Eggs of Obscure Puffer Fish, <i>Takifugu obscurus</i>

Takifugu obscurus is a euryhaline fugu species very close to Takifugu rubripes and suitable for studying osmoregulation

BackgroundThe genome sequence of the pufferfish Takifugu rubripes is an enormously useful tool in the molecular physiology of fish. Euryhaline fish that can survive both in freshwater (FW) and seawater (SW) are also very useful for studying fish physiology, especially osmoregulation. Recently we learned that there is a pufferfish, Takifugu obscurus, common name "mefugu" that migrates into FW to spawn. If T. obscurus is indeed a euryhaline fish and shares a high sequence homology with T. rubripes, it will become a superior animal model for studying the mechanism of osmoregulation. We have therefore determined its euryhalinity and phylogenetic relationship to the members of the Takifugu family.ResultsThe following six Takifugu species were used for the analyses: T. obscurus, T. rubripes, T. niphobles, T. pardalis, T. poecilonotus, and T. porphyreus. When transferred to FW, only T. obscurus could survive while the others could not survive more than ten days in FW. During this course of FW adaptation, serum Na+ concentration of T. obscurus decreased only slightly, but a rapid and large decrease occurred even in the case of T. niphobles, a peripheral fresh water species that is often seen in brackish river mouths. Phylogenetic analysis using nucleotide sequences of the mitochondrial 16S ribosomal RNA gene of each species indicated that the six Takifugu species are very closely related with each other.ConclusionT. obscurus is capable of adapting to both FW and SW. Its genomic sequence shares a very high homology with those of the other Takifugu species such that the existing Takifugu genomic information resources can be utilized. These properties make "mefugu", which has drawn little attention from animal physiologists until this study, a useful model animal for studying the molecular mechanism of maintaining body fluid homeostasis.

Salinity tolerance of embryos of obscure puffer Takifugu obscurus

Salinity tolerance of embryos of obscure puffer Takifugu obscurus was investigated at salinities of 0, 4, 8, 12, 16, 20, 24, 28, and 32 parts per thousand (ppt), respectively. Survival rates of embryos at 0, 4 and 8 ppt salinities were higher than 90% throughout the experiment, and there were no significant differences between 0 and 8 ppt ( P > 0.05), whereas most embryos died gradually at salinity of 12 ppt or higher after four days. Total hatch rates at 0, 4, and 8 ppt were 95.0%, 95.0%, and 91.0%, respectively. A few embryos hatched at salinities of 12, 16, 20, and 28 ppt; however, all larvae were deformed and died in 24 h post-hatch. Only at salinity of 8.0 ppt or lower, the embryos hatched into viable larvae. Hatching period at 0, 4, and 8 were 171, 182, and 182 h, respectively. Within the tolerable salinity range (0–8 ppt), there were no significant differences in total hatch rates, viability of 24 h post-hatch larvae, and rate of embryonic development ( P > 0.05). We concluded that embryos of obscure puffer could not tolerate salinities of 12 ppt and higher, but could well adapt to salinities below 8 ppt. Thus, it is viable to incubate embryos of obscure puffer under lower salinity conditions.

Molecular and functional characterization of adrenomedullin receptors in pufferfish

The receptors for the calcitonin gene-related peptide (CGRP)/adrenomedullin (AM) family peptides were characterized in the mefugu Takifugu obscurus, a euryhaline fugu species very close to Takifugu rubripes, which has as many as five adrenomedullin genes (AM1-5). CGRP and AM share a G protein-coupled core receptor called calcitonin receptor-like receptor (CLR), and the specificity of the CLR is determined by the interaction with receptor activity-modifying proteins (RAMPs). Through database mining, three CLRs (CLR1-3) and five RAMPs (RAMP1-5) were identified, and all of them were cloned by RT-PCR and characterized by functional expression in COS7 cells in every possible combination of CLR-RAMP. The following combinations generated cAMP in response to physiological concentrations of CGRP, AM1 (an ortholog of mammalian AM), AM2, and AM5: CLR1-RAMP1/4 (CGRP), CLR1-RAMP2/3/5 (AM1), CLR2-RAMP2 (AM1), CLR1-RAMP3 (AM2), and CLR1-RAMP3 (AM5). Their expressions were found by Northern blot analysis to be tissue specific and salinity dependent. For example, CLR1-RAMP5 and CLR1-RAMP2 are expressed specifically in the gill and kidney, respectively, suggesting their involvement in osmoregulation. Furthermore, relatively high levels of CLRs and RAMPs were found in the spleen and ovary, suggesting roles in the immune and female reproductive systems. Immunohistochemistry revealed that AM receptors of the following types are expressed in the locations, indicated in brackets, of the mefugu gill and kidney: CLR1-RAMP5 (interlamellar vessels), CLR2-RAMP2 (pillar cells), and CLR1-RAMP2 (apical side of renal proximal tubule cells).

Preliminary results on osmolality response of pufferfish Takifugu obscurus* to sudden salinity change

Preliminary results on osmolality response of pufferfish Takifugu obscurus* to sudden salinity change

Effect of temperature on incubation period and hatching success of obscure puffer Takifugu obscurus (Abe) eggs

Artificially fertilized eggs of obscure puffer Takifugu obscurus were obtained by induced spawning of cultured broodstock and incubated at temperatures of 15, 19, 23, and 27 °C. The results showed that the optimal temperature for obscure puffer embryonic development ranged from 19 to 23 °C, based on total hatch rate, viability of newly hatched larvae 24 h post-hatch, and total mortality rate of eggs. At the given temperature range, the times taken for 50% embryos to hatch were 11.3, 6.6, 5.0, and 4.2 days, respectively. There was significant difference in time to 50% hatch among the temperatures used in this experiment. The power law model, quadratic equation, exponential equation, and effective degree-day model all provided good fits for the relationship between incubation temperature and time to 50% hatch, with r 2 values greater than 0.90. The formulae for these were y=1031.7T −1.6885, y=44.721−3.1574 T+0.0615 T 2, y=34.663e −0.0813 T and y=78.905/( T−7.6033), respectively, where y is time to 50% hatch in days, and T is incubation temperature in degrees Celsius. The effective degree-day model was determined to be the best model because of efficient computation, good fit to the experimental data, and most importantly, the derived parameters, k (the sum of effective degree-days) and t 0 (the temperature of biological zero), have important biological meaning. Based on the effective degree-day model, the t 0 and k values were calculated as 7.6033 °C and 78.905 degree-days, respectively.

Induced Ovulation in Obscure Puffer Takifugu obscurus by Injections of LHRH-a

Obscure puffer Takifugu obscurus (Abedate) is one of the several species of Takifugu genus that migrate to the Yangtze River, China during the spawning season of February to May. It is a popular fish among locals and fetches a premium price owing to its high-quality meat. It is also a potential species for intensive culture as its natural populations are currently declining. There have been no published studies on the effects of GnRH-a injection on the obscure puffer. In this paper, we report the results of several obscure puffer ovulation trials conducted in 1995 and 1996. We demonstrated that ovulation could successfully be induced in obscure puffer collected from open systems during spawning period using a dosage of LHRH-a as low as 40 µg kg−1 in two injections. We found no significant differences among 80, 60, 40 µg LHRH-a kg−1 treatments in ovulation success, egg production, fertilization rate and hatch rate. Accordingly, we recommend the use of 40 µg LHRH-a kg−1 as the optimal dosage from an economical point of view.

Induced ovulation using LHRHa in anadromous obscure puffer Takifugu obscurus cultured entirely in freshwater

Puffer fishes of the order Tetradontidae exist in both anadromous and non-anadromous seawater resident forms. The obscure puffer akifugu obscurus is an anadromous species whose intensive culture in freshwater has developed rapidly in China. To mass produce larvae for intensive culture, induction of ovulation of 3-year-old obscure puffer cultured entirely in freshwater was attempted by giving the fish multiple injections of LHRHa. Twenty 3-yearold cultured obscure puffers were treated with multiple injections of LHRHa at a constant dosage of 30 μg of LHRHa kg-1 of body weight with 36 h interval between injections. Beginning two days after hormonal treatment, abdominal palpation was performed every day to check expansion and hardening of the abdomen of the fish due to hydration of oocytes that indicates the completion of final oocyte maturation. The first four fish ovulated after the second LHRHa injection on day 3, but most females ovulated after the fourth hormone injection. A total of 18 fish (90%) ovulated over a period of 7 days, while no fish ovulated in the control group. The mean fertilization rate and the mean hatch rate was 67.1% and 87.6%, respectively. The viability of newly hatched larvae was very good, with a high survival rate of 98.6% 24 h post-hatch. These results indicate that cultured obscure puffer, which are not allowed to undergo diadromous migration and are entirely cultured in freshwater, could be induced to complete maturation and ovulate by simple multiple injections of LHRHa and that the eggs could be successfully hatched into viable larvae.

Length-Weight Relationship of Obscure Puffer (Takifugu obscurus) during Spawning Migration in the Yangtze River, China

ABSTRACT Length-weight relationships were estimated for obscure puffer (Takifugu obscurus) from the Yangtze River during the spawning migration period. The formulae for all individuals, females, and males were W=0.0110SL 3.3821, W ♀=0.0119SL 3.3718 and W ♂=0.0183SL 3.2154, respectively, where W is the body weight in g and SL is the standard length in cm. Pronounced sexual dimorphism in the length-weight relationship was observed with significant difference in the allometric coefficient of the length-weight relationship between females and males. These findings indicated that the length-weight relationships of obscure puffer could be used not only to estimate weight from standard length but also to differentiate sex.

Endogenous circadian rhythm in the river puffer fish Takifugu obscurus

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 153:293-298 (1997) - doi:10.3354/meps153293 Endogenous circadian rhythm in the river puffer fish Takifugu obscurus Kim WS, Kim JM, Yi SK, Huh HT Oxygen consumption rate of 8 to 12 mo old river puffer fish Takifugu obscurus was determined using an automatic intermittent-flow-respirometer (AIFR). During the experiments, the fish were not fed and were kept in constant darkness and at constant temperature to avoid any extrinsic disturbances. It was clearly demonstrated that this species has a strong endogenous circadian rhythm in its instantaneous rates of oxygen consumption, although there were weak minor peaks of 11.4 to 11.7 h intervals. This endogenous rhythm appeared to be independent of the number of fish in the experimental chamber. The endogenous rhythm in the oxygen consumption rate observed in the present study may have profound implications for the physiological processes and biological rhythms of this species, and could also be a good reference in determining the oxygen consumption rates of other aquatic organisms. Endogenous circadian rhythm · Oxygen consumption · River puffer fish · Takifugu obscurus Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 153. Publication date: July 10, 1997 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1997 Inter-Research.

Effects of pentachlorophenol (PCP) on the oxygen consumption rate of the river puffer fish Takifugu obscurus

Effects of pentachlorophenol (PCP) on the oxygen consumption rate of the river puffer fish Takifugu obscurus

Physiological actions of taurine

Physiological actions of taurine